Multiple compressor system for refrigeration installation



y 1962 R. K. BERGER ETAL 3,033,009

- MULTIPLE COMPRESSOR SYSTEM FOR REFRIGERATION INSTALLATION Filed Jan.8, 1960 2 SheetsSheet 1 RICHARD K. BERGER ANDREW I NICHOLAS LINWOOD A.PICKLE HENRI SOUMERAI AUGUSTUS J. VAN NEWENHOVEN INVENTORS AME/ Y 1962R. K. BERGER ETAL 3,033,009

I MULTIPLE COMPRESSOR SYSTEM FOR REFRIGERATION INSTALLATION Filed Jan.8, 1960 2 Sheets-Sheet 2 FIG. 2

RICHARD K. BERGER ANDREW J'. NICHOLAS LINWOOD A.PICKLE HENRI SOUMERAIAUGUSTUS J. VAN N EWEN HOVEN INVENTORS ilnited States aware Filed Jan.8, 1960, Ser. No. 1,300 5 Claims. (Cl. 62-469) This invention relates torefrigeration installations and more particularly to multiple compressorsystems used to circulate the refrigerant in such installations.

The application of multiple compressors as the circulating means in arefrigeration system as is shown in U.S. Patent 2,076,332 has certainadvantages, both from the standpoint of manufacture and operationaleffectiveness, over single units having the capabilities of the multipleunits.

For example, shutting down a unit in the multiple system is a moreefiicient way of regulating the capacity of the system than can beaccomplished with unloaders on a single unit.

Furthermore, individual units can be added into the refrigerationinstallation along with the normal growth or expansion of the plantincluding the installation.

But inherent defects in the construction of the components of the systemand their adaptation to multiple compressor operation have createdserious operational difiiculties which have limited the application ofthese systems in refrigeration installations.

One such difliculty is presented in prior art duplex systems. Forexample, during operation with one unit the pressure in the crankcase ofthe operating compressor is usually greater than that in the suctioncompartment. As a consequence oil that collects in the suctioncompartment due to reasons well known in the art, will not return to thecrankcase where it is needed in proper quantity as lubricant.

Another operational limitation is presented in systems using more thantwo compressors, wherein one or more may be idle, as follows: the systempressure drop during foregoing operation may prevent the equalization ofoil levels in the crankcases of the individual units. As a consequenceone or more of the running units may become oil starved.

Various methods have been developed for multiple compressor systems torelieve the arresting influence that the higher gas pressure in thecrankcase compartment has on lubricant collected in the motorcompartment.

One such system is disclosed in U.S. Patent 2,869,775 and provides acompressor including check valves which prevent the buildup of abnormalpressures in the crankcase compartment, as above described, whicharrests lubricant return thereto.

An analysis of the foregoing patent indicates that the problem relativelubricant return from suction to crankcase compartment is solved butthat in providing means for destroying the system pressure to maintainsubstantially equal levels of lubricant in all of the crankcasecompartments other difiiculties are presented and particularly ininstallations including more than two compressors. In order to provide asystem of three or more units wherein the system pressure does notinterfere with the equalization of oil levels in the crankcases, it isnecessary, according to the teachings of the foregoing patent, tomaintain definite relationships between the conduits interconnecting thesuction, discharge and crankcase compartments and between check valvesmounted in the partitions of the individual compressors. Said anotherway atent ace the system contemplated by Patent 2,869,775 solves theproblem relative oil return from the suction to crankcase compartment inan individual unit but in attempt ing to provide for equalization of oillevels in all units of the system, presents technical requirements whichincrease the overall cost thereof.

In addition to insure proper operation the system contemplated in theabove patent must be operated in ac cordance with predeterminedoperational instructions which at times may be difiicult to meet.

The present invention solves both the problem of oil return from suctioncompartment to crankcase compartment and equalization of oil level inall crankcases in such manner so as not to require complex technicalconsiderations in the design or operation of the overall system.

Accordingly, it is an object of this invention to provide a multiplecompressor system for a refrigeration installation which overcomes theproblems mentioned hereinabove.

It is a further object of this invention to provide a less costlymultiple compressor system by providing standardized components whichare manufactured in accordance with assembly line techniques.

It is another object of this invention to provide a multiple compressorsystem which can be adapted to any refrigeration installation withminimum design consideration and at lowest possible cost.

With the foregoing objectives in view, and others as may appear from theaccompanying specification, the invention consists of various featuresof construction and combination of parts, which will be first describedin connection with the accompanying drawings, showing the multiplecompressor system contemplated herein, and the features of the inventionwill be specifically pointed out in the claims.

In the drawings:

FIGURE 1 is a longitudinal view in part section showing the details ofthe compressor used in the system.

FIGURE 2 is a schematic view showing a multiple compressor system.

Referring to the drawings FIGURE 1 shows a compressor generallydesignated 1, adapted for use in the multiple compressor system andembodying the novel components which provide for the return of lubricantfrom the suction to crankcase compartment and in addition maintainsubstantially equal lubricant levels in all crankcase compartments whenapplied in a multiple type system as hereinafter described.

While FIGURE 1 shows a unit of the hermetic type, it will be understoodby those familiar with this art that the concepts outlined herein may beapplied to compressors having an independent prime mover and thatreference to hermetic units hereinafter is solely for purposes ofillustration.

The hermetic compressor shown in FIGURE 1 and forming the basic elementof the multiple system resembles the unit described in United Statesapplication for Letters Patent Serial No. 742,111, now U.S. Patent2,956,730, filed June 16, 1958 by Clark B. Hamilton and Linwood A.Pickle and said compressor basically comprises a casing 2 including apartition 3 which divides same into crankcase compartment 4 and asuction compartment 5.

A crankshaft 6 supportably mounted in bearings 7 and 8 disposedrespectively in the end of the casing 2 and in the partition 3 isprovided with a jackshaft 9 which may be connected to a motor 11 asshown to provide a hermetic type unit or extend out of an end bell notshown for connection to a separate prime mover (not shown) as is wellknown in the art.

.lar to the centerline of the crankshaft.

A piston 12 is drivably connected to the crankshaft 6 by connecting rod13. The piston is slidably disposed in a cylinder 14 formed transverselyof the casing 2 and the partition 3 along an imaginary radial lineperpendicu- It will be understood that while only one cylinder is shownthat the present invention is equally applicable to multi-cylindercompressor units.

The cylinder is provided with the usual head 15 including the usualsuction and discharge valve means 16 and 17 which communicaterespectively with the suction chamber 18 and discharge outlet chamber19. As is customary fluid from the low side of the refrigerationinstallation is passed to the suction chamber through opening 20 and tothe high side of the installation from the discharge chamber 21.

Lubrication System .ervoir generally designated 31 formed in the lowerportion of the crankcase. This lubricant is pumped from the reservoir bymeans of any suitable type of pump generally designated 32 which takesits suction through the suction inlet 33 and suction line 34 having afilter 35 about the opening thereof and disposed in the lower portion ofthe reservoir. The pump is provided with a discharge outlet 36 whichcommunicates through a com- 'mon duct or passage 37 with the respectivetransverse passages 38 and 39 which feed the bearings 7 and 8respectively. Other transverse passages 3? throw fluid onto theconnecting means for the connecting rod 13 and other moving parts of theunit.

Compressors of the above described type are well known in the art andhave been incorporated in multiple systems with the provision of a checkvalve to permit lubricant collected in the suction compartment to returnto the crankcase compartment to bring the quantity of lubricant thereinto normal level as is indicated at 50 in FIGURE 1.

As was mentioned hereinabove, blowby of refrigerant tends to raise andmaintain the pressure in the crankcase compartment 4 above that in thesuction compartment 5 to arrest lubricant return to the crankcase. Thiscondition is further amplified ina multiple system, including theforegoing compressor, because the system pressure drop arrestsequalization of lubricant levels in the crankcases. As a consequence itis necessary to provide some positive means for returning the lubricantfrom the suction compartment 5 and for destroying the effects of thesystem pressure drop which tends to arrest equalization of lubricantlevels in the crankcase compartments.

The system pressure drop is destroyed with the provision of an orifice51 in the partition 3 and conduit means 52 interconnecting the crankcasecompartments so that the bottom of the conduit 52 opens into thecrankcase at the normal lubricant level as shown at 53 and by providingan area ratio of at least 125 to 1 between the conduit and orifice.

With the foregoing provision the crankcases are at a pressure levelbetween the higher suction pressure of the idle compressors and thelower suction pressure of the running units and accordingly lubricanttends to flow to equal levels in all crankcases.

While the above features, namely the coacting orifice and conduit,relieve the system from the problems caused by the system pressure dropit is pointed out that there results a higher pressure in the crankcasethan in the suction compartment of the running unit. This is not aserious operational drawback bacause provision as above described willpermit. equalization of. lubricant in... all

crankcases to prevent any one unit from becoming starved of same.However in practice it is desirable to provide means for returninglubricant from the low pressure suction compartment to the high pressurecrankcase compartment of the running units.

This is accomplished by means of an ejector generally designated 60which is described in greater detail in above Patent No. 2,956,730 andshown as including a suction inlet 61 connected to the partition 3 sothat the inlet is disposed at a predetermined point in the partition formaintaining the level of collected oil in the motor compartment at thedesired level as is shown at 62. The suction chamber communicates withthe discharge outlet 63 which is disposed as shown in FIGURE 1 todischarge motive fluid onto the moving parts of the crankcase and pistonassembly. The motive fluid is delivered to the ejector by means of afeed line 64 connected by any suitable connecting means 65 to the pump32 at one end and at the other end by any suitable connecting means tothe discharge portion of the ejector 61. Thus, means are provided todeliver motive fluid through the ejector in a manner well known in theart.

The apparatus described above thusly permits the adaptation of thecompressor 1, which in itself. is an advance as it solves the oil returnproblem present in individual installations, into a multiple systemWithout the necessity of incorporating complex design changes.

A multiple compressor system including the above compressor is shown inFIGURE 2 and can be readily assembled by interconnecting the suctionchambers 5 through conduit means 55 with the low side oftherefrigeration installation .as will be readily understood by thoseskilled in this art. 'In similar fashion the discharge compartments 21are interconnected by conduit means 56 with the high side of theinstallation.

Conduit 52 of a predetermined dimension relative the orifice 51interconnects the crankcases to provide means for passing lubricant fromcrankcase to crankcase to provide equalization of level thereinregardless of the sequence of operation of compressors.

Thusly with the above provisions applicant describes a multiplecompressor system which eliminates the objections of prior type unitsand it will be evident to those skilled in the art that many changes maybe made without departing from the scope of the appended claims.

What is claimed is:

1. A multiple compressor system for use in a refrigeration installationand including a plurality of compressors, each compressor comprising acasing including a partition therein dividing said easing into a suctioncompartment and a crankcase compartment, a discharge compartment in thecasing, a lubrication system for said compressor and disposed in saidcasing, a suction conduit interconnecting each of the suctioncompartments and said conduit connected to the low side of therefrigeration installation, a discharge conduit interconnecting each ofthe discharge compartments and said discharge con duit connected to thehigh side of said refrigeration installation, an opening in thepartition of each compressor to permit fluid to pass there through tomaintain substantially equal pressures in both the suction and crankcasecompartments, ejector means including a suction inlet and a dischargeoutlet disposed in the partition, the suction inlet of the ejector meanscommunicating with the suction compartment, the discharge outlet of saidejector means being disposed in the crankcase compartment, meansinterconnecting the ejector with the lubrication system of saidcompressor whereby upon operation of the compressor said ejector willpass fluid from the suction compartment to the crankcase compart ment,and a conduit interconnecting the crankcase compartments of each of saidcompressors.

2. A multiple compressor system for use in a refrigeration installationand including a plurality of compressors, each compressor comprising acasing including a partition therein dividing said easing into a suctioncompartment and a crankcase compartment, a discharge compartment in thecasing, a lubricating system including a pump means for the compressorand disposed in the casing, a suction conduit interconnecting each ofthe suction compartments and said suction conduit connected to the lowside of the refrigeration installation, a discharge conduitinterconnecting each of the discharge compartments and said dischargecompartment connected to the high side of said installation, an orificeof a predetermined size in the partition of each of said compressors topermit fluid to pass therethrough to maintain substantially equalpressures in the suction and crankcase compartments, ejector meansincluding a discharge outlet and a suction inlet disposed in saidpartition, said suction inlet communicating with the suctioncompartment, said discharge outlet communicating with the crankcasecompartment, means connecting the discharge outlet of the ejector to thepump of the lubrication system whereby during operation of the pumpmeans said ejector passes fluid from the suction compartment to thecrankcase compartment, and a conduit of predetermined dimensioninterconnecting the crankcase compartment of each of said compressors.

3. A multiple compressor system for use in a refrigeration installationand including at least three compressors, each compressor comprising acasing including a partition therein dividing said easing into a suctioncompartment and a crankcase compartment, a discharge compartment in thecasing, a lubrication system including a pump means for the compressorand disposed in the casing, a suction conduit interconnecting each ofthe suction compartments and said suction conduit connected to the lowside of the refrigeration system, a discharge conduit interconnectingeach of the discharge compartments and said discharge conduit connectedto the high side of said refrigeration installation, an orifice of apredetermined dimension in the partition of each corn-pressor to permitfluid to pass therethrough to maintain substantially equal pressures inboth suction and crankcase compartments, and ejector means including asuction inlet and a discharge outlet disposed in said partition, saidsuction inlet disposed in said partition at a predetermined point and incommunication with the suction compartment for maintaining a desiredlevel of lubricant in said suction compartment, and said dischargeoutlet disposed in the crankcase compartment at a predetermined point,means connecting the discharge outlet of the ejector to the pump meansof the lubrication system whereby during operation of the pump meanssaid ejector will pass fluid from the suction compartment to thecrankcase compartment and direct said fluid adjacent the point ofconnection between the crankshaft and the connecting rod, and a conduitinterconnecting the crankcase compartment of each of said compressors.

4. The system claimed in claim 3 wherein the bottom of the conduitinterconnecting the crankcases is connected to the crankcases at thenormal lubricant level.

5. The system claimed in claim 4 wherein the ratio of areas between themeans in the casing providing communication between the suction andcrankcase compartments and the conduit connecting the crankcases is atleast to 1.

References Cited in the file of this patent UNITED STATES PATENTS1,948,572 Floyd Feb. 27, 1934 1,954,498 Smith Apr. 10, 1934 2,048,025Phillip July 21, 1936 2,076,332 Zercher Apr. 6, 1937 2,128,388 WilliamsAug. 30, 1938 2,145,354 Hull Jan. 31, 1939 2,150,487 Brown Mar. 14, 19392,191,326 Smith, et al. Feb. 20, 1940 2,274,774 Chambers Mar. 3, 19422,738,652 Phillip Mar. 20, 1956 2,869,775 Neubauer Jan. 20, 19592,956,730 Hamilton et a1. Oct. 18, 1960 OTHER REFERENCES TraneRefrigeration Manual, Trane Company, La Crosse, Wis. Copyright 1946(pages 17-18).

